JP3371200B2 - Display control method of liquid crystal display device and liquid crystal display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a display control method thereof, and more particularly, to a color light source type liquid crystal display device for performing full-color display by time-divisionally emitting three primary color backlights and its display control. Regarding the method.

[0002]

2. Description of the Related Art With the recent development of so-called office automation, OA equipment represented by word processors, personal computers and the like has been widely used. Further, with the widespread use of OA equipment in such offices, there is a demand for portable OA equipment that can be used both in the office and outdoors, and there has been a demand for making them smaller and lighter. A liquid crystal display device is widely used as one of means for achieving such an object.
In particular, the liquid crystal display device is an indispensable technology not only for downsizing and weight reduction but also for low power consumption of battery-powered portable OA equipment.

By the way, liquid crystal display devices are roughly classified into a reflection type and a transmission type. The reflective type is a structure in which light rays incident from the surface of the liquid crystal panel are reflected on the bottom surface of the liquid crystal panel and the image is visually recognized by the reflected light, and the transmissive type is a light source (backlight) provided on the bottom surface of the liquid crystal panel. This is a configuration in which an image is visually recognized with transmitted light. The reflective type is inferior in visibility because the amount of reflected light is not constant depending on environmental conditions, but it is inexpensive, so a single color (for example, white /
Although it is widely used as a display device for black display, etc., it is not suitable for a display device such as a personal computer for multi-color or full-color display. Therefore, a transmissive type is generally used as a display device such as a personal computer for multi-color or full-color display.

On the other hand, the current color liquid crystal display device has STN (Super Twisted Nematic) in view of the liquid crystal material used.
Type and TFT-TN (Thin Film Transistor-Twisted Nemati
c) Type is generally classified. The STN type has a relatively low manufacturing cost, but has a problem that it is not suitable for displaying moving images because crosstalk is likely to occur and the response speed is relatively slow. On the other hand, the TFT-TN type is STN
Although the display quality is higher than that of the type, since the transmittance of the liquid crystal panel is currently only about 4%, a high brightness backlight is required. For this reason, the TFT-TN type consumes a large amount of power due to the backlight and has a problem in using it in a battery-powered portable type. In addition, the TFT-TN type has other problems such as a slow response speed, particularly a slow halftone response speed, a narrow viewing angle, and difficulty in color balance adjustment.

Further, the conventional transmissive liquid crystal display device uses a white light backlight and is configured to perform multi-color or full-color display by selectively transmitting the white light with color filters of three primary colors. The color filter type was common. However, in such a color filter type, since the display pixel is configured with the range of the color filters of three adjacent colors as one unit, the resolution is substantially reduced to 1/3.

[0006]

As described above, in the conventional liquid crystal display, especially in the color liquid crystal display, STN has a relatively low manufacturing cost, but crosstalk is likely to occur and the response speed is relatively low. It has a low speed and therefore has problems such as being unsuitable for displaying moving images. In addition, the TFT-TN requires a high-intensity backlight, so it consumes a large amount of power. There are problems such as slowness, narrow viewing angle, and difficulty in color balance.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a color liquid crystal display having excellent response speed and viewing angle characteristics, and variable color balance.

The present invention also solves the problem of time-divisional color liquid crystal displays, in which almost half of the light emission time of the backlight is not used and there is much waste in terms of efficiency and power consumption. Also aim.

[0009]

[Means for Solving the Problems] From the above viewpoints,
In the liquid crystal display device and the display control method thereof according to the present invention,
Synchronize liquid crystal switching and backlight emission by combining a liquid crystal panel using a ferroelectric liquid crystal that can respond on the order of 0 to several μs with a backlight that can emit red, green, and blue in a time-division manner. Then, color display is performed, and at that time, writing scanning of pixel data to the ferroelectric liquid crystal panel is performed twice during a sub-frame period in which each color of red, green and blue emits light. However, the first writing scan is performed so that the image is displayed, and the second writing scan is performed so that the image display state is erased.

Further, in the first writing scan and the second writing scan, control is performed so that electric fields having the same intensity but opposite polarities are applied to the respective pixels of the liquid crystal panel.

Further, in the second writing scan, when a voltage is applied to each pixel of the liquid crystal panel, the polarization axis is orthogonal to the molecular long axis direction (optical axis) of almost all the ferroelectric liquid crystal molecules. The liquid crystal panel is configured so that the polarization axis of either one of the two polarizing plates installed so as to sandwich the panel is aligned. Alternatively, the polarity of the voltage applied to each pixel is optimized so that such a state is realized. This reduces light leakage from the backlight during the period when each pixel is in the non-display state.

Further, in the liquid crystal display device and the display control method of the present invention, the light emitting area of the backlight is divided into at least two light emitting areas, which is synchronized with the writing / erasing scanning of the pixel data to the liquid crystal panel. The light is turned on and off. As a result, the period in which the backlight emits light wastefully decreases, and power consumption is reduced.

Furthermore, the backlight is made to emit light only during the period from the end of the writing scan of the pixel data to the liquid crystal panel to the start of the erasing scan. This makes it possible to contribute all of the light emission amount of the backlight to the display.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof.

FIG. 1 is a block diagram of a constitutional example of a liquid crystal display device according to the present invention, FIG. 2 is a schematic sectional view of a liquid crystal panel and a backlight thereof, and FIG. 3 is a schematic diagram showing a constitutional example of a liquid crystal panel and a backlight. FIG. 4 is a schematic perspective view, and FIG. 4 is a schematic view showing a configuration example of an LED array which is a light source of a backlight.

In FIG. 1, reference numerals 21 and 22 respectively denote a liquid crystal panel and a backlight whose sectional structure is shown in FIG. As shown in FIG. 2, the backlight 22 includes the LED array 7 and the light guide plate + light diffuser plate 6.
It is composed of.

The liquid crystal panel 21 is constructed as a structure between two polarizing films 1 and 5 as shown in FIGS. Specifically, the liquid crystal panel 21 is laminated in order from the upper side to the lower side of the polarizing film 1, the glass substrate 2, the common electrode 3, the glass substrate 4, the polarizing film 5, the light guide plate + the light diffusion plate 6, Common electrode 3 on glass substrate 4
Pixel electrodes 40 corresponding to individual display pixels arranged in a matrix are formed on the side surface. A liquid crystal drive control means 50 including a data driver 32 and a scan driver 33, which will be described later, is connected between the common electrode 3 and the pixel electrode 40. The individual pixel electrodes 40 are
On / off control is performed by a TFT (Thin Film Transistor), and each TFT is driven by selectively turning on / off a signal line by a data driver 32 and a scanning line by a scan driver 33. Then, the transmitted light intensity of each pixel is controlled by the signal from the signal line.

An alignment film 12 is disposed on the upper surface of the pixel electrode 40 on the glass substrate 4, and an alignment film 11 is disposed on the lower surface of the common electrode 3, and a liquid crystal material is filled between both alignment films to form a liquid crystal layer. 13 is formed. Incidentally, reference numeral 14 is a liquid crystal layer 13
Is a spacer for appropriately maintaining the layer thickness of.

The backlight 22 is located in the lower layer of the liquid crystal panel 21, and is provided with the LED array 7 in a state of protruding from one side of the light guide plate + the light diffusion plate 6 forming the light emitting region. As shown in the schematic view of FIG. 4, this LED array 7 has three primary colors, that is, red, on the surface facing the light guide plate + light diffusion plate 6.
The LEDs emitting the respective colors of (R), green (G), and blue (B) are arranged sequentially and repeatedly. Light guide plate + light diffusion plate 6 is this LED
The light emitted from each LED of the array 7 functions as a light emitting region by guiding the light to the entire surface of itself and diffusing it to the upper surface.

In FIG. 1, image data 30 is supplied with display data DD to be displayed by the liquid crystal panel 21 from an external device such as a personal computer. The image memory 30 temporarily stores the display data DD in the image memory, and then data for each pixel (hereinafter referred to as pixel data PD).
Is output in synchronization with the synchronization signal SYN generated by the control signal generation circuit 31. The pixel data PD output from the image memory 30 is input to the selector 37 as it is and is also applied to the inverse data generation circuit 36.

The inverse data generating circuit 36 is a circuit for generating inverse data of the pixel data PD output from the image memory 30, and the output signal thereof is the inverse pixel data #PD as the selector 37.
Given to. Therefore, the pixel data PD output from the image memory 30 and the inverse pixel data #PD output from the inverse data generation circuit 36 are input to the selector 37, and one of them is selected according to the control signal CS given from the control signal generation circuit 31. Is output to the data driver 32.

The data driver 32 turns on / off the signal line of the pixel electrode 40 to output pixel data output from the selector 37.
Control according to PD or inverse pixel data #PD.

The control signal generation circuit 31 outputs a synchronization signal.
SYN is output and supplied to the scan driver 33, the reference voltage generation circuit 34, the backlight control circuit, and the drive power supply 35.

The scan driver 33 is a control signal generation circuit 31.
The pixel electrode 40 is synchronized with the synchronization signal SYN given by
ON / OFF of the scanning line of Further, the reference voltage generation circuit 34 generates the reference voltage VR in synchronization with the synchronization signal SYN,
The data driver 32 and the scan driver 33 are provided.

The backlight control circuit and drive power supply 35 are
The drive voltage is supplied to the backlight 22 in synchronization with the synchronization signal SYN supplied from the control signal generation circuit 31
The LED array 7 of is made to emit light.

The display operation of the liquid crystal display device of the present invention will be described below. FIG. 5 shows the light emission timing of the LEDs of each color of the backlight 22 and the scanning timing of each line of the liquid crystal panel 21 for explaining the principle of the first embodiment of the display control method of the liquid crystal display device of the present invention. It is a time chart which shows a relationship.

As shown in FIG. 5 (a), the LEDs of the backlight 22 are made to sequentially emit light in the order of red, green, and blue, for example, every 5.6 ms, and each pixel of the liquid crystal panel 21 is synchronized with that. The display is performed by switching in line units.
When displaying 60 frames per second, the period of one frame is 16.6 ms, and the period of one frame is further divided into 3 sub-frames of 5.6 ms each, and the red light of the backlight 22 is divided in each sub-frame. , Green, blue LEDs
For example, in the example shown in Fig. 5 (a), a red LED is used in the first subframe, a green LED is used in the second subframe, and a blue LED is used in the third subframe. Light is emitted under the control of the backlight control circuit and the driving power supply 35, respectively.

As described above, each sub-frame has 5.6
When 1 frame is set to 16.6 ms, about 60 frames can be displayed per second, so that the flicker of the display is not generally recognized by human eyes. However, this is merely an example, and it goes without saying that 30 frames per second may be displayed as in television broadcasting, for example.

On the other hand, as shown in FIG. 5 (b), the data driver 32 and the scan driver 33 cause the liquid crystal panel 21 to write and scan data into the red, green, and blue subframes. Do twice. However, the start timing of the first write scan (write timing to the first line) matches the start timing of each subframe, and the end timing of the second write scan (write timing to the last line) is set. The timing is adjusted so as to coincide with the end timing of each subframe.

Further, in the first write scan, the control signal generation circuit 31 causes the selector 37 to output the pixel data PD by the control signal CS, and the signal of the voltage corresponding to the pixel data PD output from the selector 37 is generated. By being supplied from the data driver 32 to each pixel of the liquid crystal panel 21, an electric field is applied, the transmittance is adjusted, and an image corresponding to the pixel data PD is displayed. As a result, full color display is performed.

Then, in the second writing scan,
The control signal generation circuit 31 causes the selector 37 to output the inverse pixel data #PD by the control signal CS, and the voltage signal corresponding to the inverse pixel data #PD output from the selector 37 is transmitted from the data driver 32 to each of the liquid crystal panels 21. Supplied to the pixel. As a result, an electric field having the same strength as the electric field applied to each pixel at the time of the first writing scan and having the opposite polarity is applied to each pixel of the liquid crystal panel 21. As a result, the display of each pixel of the liquid crystal panel 21 is erased.

In the conventional liquid crystal display device, once the pixel data is
After the PD is written, the control for erasing the PD is not performed, but the control for directly overwriting the next pixel data PD has been performed. However, in the present invention, the above-described pixel data PD is written and then erased by the inverse pixel data #PD at a predetermined time interval, so that the display of all the pixels on the screen of the liquid crystal panel 21 is performed. Since the time, in other words, the time during which the liquid crystal is in the display state in each pixel is the same, no brightness unevenness occurs.

The voltage of the signal supplied to each pixel of the liquid crystal panel 21 in the first writing scan and the second writing scan is the same in magnitude but different in polarity. The application is prevented.

By the way, since the ferroelectric liquid crystal has polar responsiveness, whether the incident light is transmitted or shielded is determined depending on the polarity of the applied voltage, and further, it has a memory property for maintaining the state. Therefore, when a voltage is applied to each pixel by the second scanning within one sub-frame, which is a feature of the present invention as described above, the relationship between the polarization axes of the polarizing films 1 and 5 and the liquid crystal molecule long axis direction. Or, if the polarity of the applied voltage is not optimum, the backlight light cannot be completely shielded and color mixing occurs, or a desired color cannot be displayed and the image quality deteriorates.

Under such circumstances, according to the present invention, when a voltage is applied to each pixel of the liquid crystal panel 21 in the second writing scan, as shown in the schematic diagram of FIG. The long axis direction (optical axis) of the liquid crystal molecules is aligned with the polarization axis of either one of the two polarizing films 1 and 5 that are installed so as to sandwich the panel and have the polarization axes orthogonal to each other. By configuring the liquid crystal panel 21 or optimizing the polarity of the voltage applied to each pixel, the same state is maintained and the displayed image is surely erased.

Next, specific examples of the liquid crystal display device and the display control method thereof according to the present invention will be described.

First, the liquid crystal panel 21 shown in FIGS. 2 and 3 was produced as follows. A TFT substrate was prepared with individual pixel electrodes 40 having a pitch of 0.24 mm × 0.24 mm and a matrix of 1024 × 768 pixels and a diagonal of 12.1 inches. After cleaning such a TFT substrate and the glass substrate 2 having the common electrode 3, polyimide is applied by a spin coater and baked at 200 ° C. for 1 hour to obtain about 200Å
The polyimide film of was formed as the alignment films 11 and 12. Furthermore,
Rubbing these alignment films 11 and 12 with a rayon cloth,
An empty panel was manufactured by stacking the two with a spacer 14 made of silica having an average particle diameter of 1.6 μm and holding a gap therebetween. A ferroelectric liquid crystal containing naphthalene-based liquid crystal as a main component was sealed between the alignment films 11 and 12 to form a liquid crystal layer 13.

[0038] Then, the produced panel was made into two polarizing films in a crossed nicols state (manufactured by Nitto Denko: NPF-EG1225DU).
The liquid crystal panel 21 is sandwiched between the liquid crystal layers 1 and 5 so that when the ferroelectric liquid crystal molecules of the liquid crystal layer 13 are tilted to one side, they are in a dark state. Then, the liquid crystal panel 21 was placed on the backlight 22, that is, the light guide plate + the light diffusion plate 6.

The liquid crystal panel 21 manufactured as described above is
Display control was performed as shown in the timing chart of FIG. 7 in the configuration mounted on the backlight 22 composed of the LED array 7 and the light guide plate + light diffusion plate 6.

1 for 16.6 ms as shown in FIG. 7 (a)
In the red, green, and blue subframe periods that divide the frame period into three equal parts, as shown in Fig. 7 (b),
The writing scan for each pixel of the ferroelectric liquid crystal panel 21 was performed twice for each line.

First, the first write scan is adjusted while adjusting the timing so that the start timing of the write scan on the first line (line 1) of the liquid crystal panel 21 coincides with the start timing of each sub-frame. A signal of a voltage corresponding to each pixel data PD is applied to each of 21 pixels from the data driver 32 in a line unit. The first application of the voltage to each pixel is performed at timings sequentially deviated by a predetermined time from the first line to the last line.

As a result, as shown in FIG. 7 (c), each pixel of the liquid crystal panel 21 is turned on line by line. The lighting of each pixel is sequentially performed from the first line to the final line at a timing shifted by a predetermined time.

The second writing scan is performed on each pixel of the liquid crystal panel 21 while adjusting the timing so that the end timing of the writing scan to the final line of the liquid crystal panel 21 coincides with the end timing of each sub-frame. A signal having the same voltage as the signal applied in the first writing scan but different polarity is applied to each of them from the data driver 32 on a line-by-line basis. As in the case of the first time, the second voltage application to each pixel is performed at timings that are sequentially deviated by a predetermined time from the first line to the last line. However, as described above, each subframe ends. Specifically, the timing of starting the second voltage application to the first line is adjusted so that the timing of ending the writing scan to the final line of the liquid crystal panel 21 coincides with the timing.

As a result, as shown in FIG. 7C, each pixel of the liquid crystal panel 21 is turned off in a line unit. The transition of each pixel to the non-illuminated state is performed at timings sequentially deviated by a predetermined time from the first line to the final line.

Further, as shown in FIG. 6 described above,
When a voltage is applied to each pixel of the liquid crystal panel 21 in the second writing scan, the polarization axes of two sheets of polarization are orthogonal to the molecular long axis direction (optical axis) of almost all ferroelectric liquid crystal molecules. The configuration of the liquid crystal panel 21 was optimized so that the polarization axis of either one of the films 1 and 5 would match. In particular,
The polarization directions of the two polarizing films 1 and 5 whose polarization axes are orthogonal to each other are optimized.

With respect to the liquid crystal panel 21 having the above configuration
With the device configuration as shown in FIG.
By controlling the display, the display area of the liquid crystal panel 21
There is no brightness unevenness over the entire area,
Realizes a high-quality image display state with no color mixture due to external display colors
I was able to manifest. The brightness of white display is 192 cd / m ² 
And the contrast ratio was 35: 1.

Although the polarization directions of the two polarizing films 1 and 5 whose polarization axes are orthogonal to each other are optimized in the above-mentioned embodiment, the voltage is applied to each pixel of the liquid crystal panel 21 in the second writing scan. When applied, almost all of the ferroelectric liquid crystal molecules have a molecular long axis direction (optical axis) that matches the polarization axis of either one of the two polarizing films 1 and 5 whose polarization axes are orthogonal to each other. Thus, the polarity of the applied voltage may be adjusted.

Furthermore, in the above embodiment,
Although the ferroelectric liquid crystal is used for the liquid crystal panel 21, it goes without saying that the same effect can be obtained also in a liquid crystal display using a liquid crystal substance other than the ferroelectric liquid crystal, for example, an antiferroelectric liquid crystal.

By the way, in the time-division color liquid crystal display as described above, the backlight 22, more specifically, L
In the worst case of the light emission amount of the ED array 7, only half of the light emission amount is used, which is wasteful in terms of power consumption. This means that portable OA, which is often used on battery
It is a serious problem for equipment. Therefore, in the display control method as described above, it is possible to further reduce the power consumption.
The embodiment will be described.

The time chart of FIG. 8 shows the amount of light emitted from the backlight 22 and the liquid crystal panel 21 in the first embodiment.
Shows the relationship with the display state. As shown in Fig. 8 (a), in the 5.6ms subframe period, the first voltage application starts at the same time as the start of the subframe and continues for the subsequent 2.8ms period. Is applied from the beginning of the subframe
The process is started from the time point when 2.8 ms has elapsed and continues for the subsequent 2.8 ms period, that is, until the end time point of the subframe.

In such a case, as shown in FIG. 8 (b), the time during which a pixel is lit is 1 subframe of 1 subframe in one subframe of a period of 5.6 ms. Only / 2. Therefore, as shown in FIG. 8A, the light emission time in which the backlight 22 contributes to the actual display is 1/2, and the remaining 1/2 is shielded and wasted. In this case, if the scanning time of the liquid crystal panel is possible in a time shorter than 2.8 ms shown in FIG. 8, the utilization efficiency of the backlight 22 is improved, but in the current TFT made of amorphous silicon, the mobility is high. It is too low to expect a significant reduction in scanning time.

In order to solve such a problem, in the second embodiment of the present invention, the light emitting area of the backlight 22 is divided into at least two, and writing / erasing of data to / from the liquid crystal panel 21 is performed. The switching of light emission and light extinction is performed in synchronization with scanning.

First, the principle will be described. FIG. 9 is a schematic diagram showing an example in which the light emitting area of the backlight 22 is equally divided into four blocks. In this example, the light guide plate +
The light diffusing plate 6 is provided along the line direction of the liquid crystal panel 21 with a light-shielding film to form a strip-like uniform light emitting region (1) 221-light emitting region (4)
It is divided into 4 into 224, and the LED array 7 is also LE
It is divided into four D array blocks 71 to 74. Each LED array block 71-74 includes at least one LED array block and the same number of red, green, and blue LEDs.
(1) 221 is the light emitting area by the LED array block 71 (2)
222 is the light emitting area (3) 223 due to the LED array block 72
LED array block 73 causes the light emitting area (4) 224 to be L
Light emission is controlled by the ED array block 74.

Display control according to the second embodiment of the present invention when the backlight 22 is provided will be described with reference to the time chart of FIG.

As shown in FIG. 10, the liquid crystal panel 21
The backlight 22 is turned on and off in synchronization with the scanning of. More specifically, during the period in which each line of the liquid crystal panel 21 corresponding to the light emitting area 221 of the backlight 22 is being scanned, the LED array block 71 is caused to emit light to emit light.
The LED array block 72 is made to emit light while each line of the liquid crystal panel 21 corresponding to 222 is scanned, and the LED array block 73 is made to emit while each line of the liquid crystal panel 21 corresponding to the light emitting region 223 is scanned. The LED array block 74 is caused to emit light during a period in which each line of the liquid crystal panel 21 corresponding to the light emitting area 224 is being scanned.

Therefore, for example, the period of each red, green, and blue sub-frame is 5.6 ms, and data writing / writing to the liquid crystal panel 21 is performed.
If the erase scan time is 2.8 ms each,
The light emission time within a subframe of 1 to 224 is 3.5 ms, which can be reduced to 62.5% compared to 5.6 ms in the case shown in FIG. In other words, the power consumption is about 3
It is possible to save 7.5%. At this time, the liquid crystal panel 2
The time for which each pixel of 1 is in the display state (data writing state) is 2.8 ms as in the first embodiment, and does not affect the display brightness. On the contrary, originally, it is a problem that the light from the backlight 22 does not leak to the surface of the liquid crystal panel 21,
That is, in the period in which each pixel of the liquid crystal panel 21 is in the non-display state, the period in which the backlight 22 is turned off becomes longer.
(In the above-described embodiment, the backlight 22 is off at 0%). Therefore, the contrast ratio and the display color purity are further improved.

Table 1 below shows the relationship of the ratio of the light emission time when the light emitting region of the backlight 22 is divided and when the light emitting region is not divided.

[0058]

[Table 1]

As is apparent from Table 1, as the number of divisions of the light emitting area of the backlight 22 is increased, the light emitting time of each light emitting area in each subframe period becomes shorter. Here, assuming that the number of divisions of the light emitting region is N _B , the ratio R of the light emission time with respect to the case of non-division is expressed by the following equation, and approaches 50% as the number of division N _B of the light emitting region increases. Therefore,
The larger the division number N _B of the light emitting area is, the larger the maximum
It is possible to significantly reduce power consumption up to 50%. R = 0.5 + 1 / (2 · N B)

In the above description, the backlight
It is needless to say that the light emission time is evenly divided according to the number of divisions of the 22 light emitting regions and the light emission / extinguishing timings do not overlap, but they may overlap as necessary.

Next, a concrete example of the second embodiment of the present invention as described above will be described. The liquid crystal panel 21 used here is the same as the liquid crystal panel 21 used in the above-mentioned embodiment. The same display control was performed as shown in the time chart of FIG.

As shown in FIG. 11 (a), in each of the light emitting areas 221, 222, ... Of the backlight 22, first, red light is sequentially emitted for a predetermined time in a period of one subframe. Be done. Then, as shown in FIG. 11B, while the light emitting area 221 of the backlight 22 is emitting light, writing / erasing scanning of pixel data is performed on the line of the liquid crystal panel 21 corresponding to the area, Specifically, the pixel data PD is written / the reverse pixel data #PD is written and scanned. That is, the light emission control of each light emitting area 221, 222 ... Of the backlight 22 and the data writing / erasing scanning for each line of the liquid crystal panel 21 are controlled in synchronization. As a result, as shown in FIG. 11 (c), the display is performed by realizing each pixel of the liquid crystal panel 21 in the lit or unlit state.

Thereafter, display control is similarly performed in each of the periods of the green subframe and the blue subframe, and one frame is completed. By repeating such control of one frame, it is possible to display 60 frames per second.

In such an embodiment, it was possible to realize a clear full-color display with excellent color purity. In the time-sharing color display, the time for each red, green, and blue subframe is 5.6 ms, the data writing / erasing check time for the LCD panel 21 is 2.8 ms, and the light emitting area of the backlight 22 is divided into 4 blocks. The emission time of each emission region 221, 222, 223, 224 could be shortened to about 3.5 ms. At this time, the emission brightness of the backlight 22 alone is 631 cd / m ² , and the brightness when the white display is performed in combination with the liquid crystal panel 21 is 190.
It was cd / m ² and the contrast ratio was 43: 1. The utilization efficiency of the light emission amount of the backlight 22 was about 30%. In addition,
When the power consumption of the backlight 22 was examined, it was 19 W.

As another embodiment, a liquid crystal panel similar to the above
21 is used, the backlight 22 is divided into 10 equal light emitting areas 221, 222, ... Further, the time of each red, green, and blue sub-frame is 5.6 ms, and the data writing / erasing scanning time to the liquid crystal panel 21 is set. The actual display control was performed for each 2.8 ms.

In this case, the light emitting area of the backlight 22 is set to 10
By dividing into the individual light emitting regions 221, 222, ..., It was possible to reduce the light emitting time of each light emitting region 221, 222 ,. At this time, the emission brightness of the backlight 22 alone was 560 cd / m ² , the brightness when white display was performed in combination with the liquid crystal panel 21, was 194 cd / m ² , and the contrast ratio was 51: 1. . The utilization efficiency of the amount of light emitted by the backlight 22 was increased to about 35%. When the power consumption of the backlight 22 was examined, it was 16 W, which was even lower than that in the above-mentioned embodiment.

Thus, in this embodiment, the backlight 22 is used.
By increasing the number of divisions of the light emitting area, the contrast ratio was improved and the power consumption was reduced while obtaining the white level equivalent to that of the above-described embodiment.

Here, as a comparative example to the above-mentioned two examples, the same liquid crystal panel 21 as those was used, and the backlight 22 was not divided and the display control was performed.

In this example, when the light emission of the backlight 22 is controlled in synchronization with the data writing / erasing scanning of the liquid crystal panel 21 to perform color display in time division, the color purity is excellent.
A clear color display was obtained, but when the time (light emission time) of each red, green, and blue subframe was 5.6 ms and the data write / erase scan time of the liquid crystal panel 21 was 2.8 ms each, the The light emission brightness of the light 22 alone was 1009 cd / m ² , and the brightness when white display was performed in combination with the liquid crystal panel 21 was 192 cd / m ² , and the contrast ratio was 35: 1. The usage efficiency of the amount of light emitted from the backlight 22 is about 19%.
The power consumption of the backlight 22 was 31 W, which was higher than that of any of the examples in which the light emitting region of the backlight 22 was divided.

As described above, when the light emission control of the backlight 22 is performed without dividing the light emission area, the white level is the same as that of the above two embodiments, but the contrast ratio is low. Power consumption also increases.

Although the ferroelectric liquid crystal is used for the liquid crystal panel 21 in the above-mentioned respective embodiments and comparative examples, the same applies to liquid crystal displays other than the ferroelectric liquid crystal, for example, antiferroelectric liquid crystal. It goes without saying that the effect can be obtained.

As described above, when the light emitting area of the backlight 22 is evenly divided and sequentially emitted, and the data write / erase scanning is synchronized with each line of the liquid crystal panel 21 corresponding to each As described above, the utilization efficiency of the emission time of the backlight 22 gradually approaches 100% as the number of divisions of the emission area of the backlight 22 increases.
Not 0%. Therefore, if 100% of the light emission time of the backlight 22 is used, in other words, control is performed so that the backlight 22 emits light only for the time that contributes to the display, it is very useful for battery-powered portable OA devices. Be beneficial.

FIG. 12 is a time chart of such display control according to the third embodiment of the present invention. In the third embodiment, the light emitting area of the backlight 22 is one as in the first embodiment.

Here, as shown in FIG. 12B, for each pixel of the liquid crystal panel 21, the red, green, and blue colors in one frame period are set in the same manner as in the above-described embodiments. In each sub-frame, scanning for writing data in units of lines and scanning for erasing data by applying a voltage having the same polarity as that applied but having a reverse polarity are performed, as shown in FIG. 12 (a). LCD panel 21 in each sub-frame
The light emission is started at the time when the writing of the data to the last line is finished, and is stopped before the time when the erasing of the data of the first line of the liquid crystal panel 21 is started in each sub-frame. In other words, the backlight 22 is controlled to emit light only in a period in which all pixels of the liquid crystal panel 21 are in the display state in each subframe. As a result, 100% of the light emission time of the backlight 22 contributes to the light emission display by the liquid crystal panel 21.

Next, a concrete example of the third embodiment will be described. The liquid crystal panel 21 used here is almost the same as that used in each of the above-described embodiments (the same except that the scanning of the TFT can be divided into upper and lower halves), so the description thereof is omitted and the time chart of FIG. 13 is used. Display control was performed as shown.

As shown in FIG. 13B, first, in the red sub-frame, writing of pixel data PD / writing scanning of reverse pixel data #PD is performed for each line of the liquid crystal panel 21. Then, as shown in FIG. 13 (a), in the period from the time when the writing of the pixel data PD to all the lines of the liquid crystal panel 21 is completed to the time when the writing of the reverse pixel data #PD is started, the backlight 22 Light up. As a result, as shown in FIG. 13 (c), the liquid crystal panel 21
The display is performed by realizing each pixel in the ON and OFF states.

Thereafter, display control is similarly performed in each of the periods of the green subframe and the blue subframe, and one frame is completed. By repeating such control of one frame, it is possible to display 60 frames per second.

In such an embodiment, it was possible to realize clear full-color display with excellent color purity. In the time-division color display, the time for each red, green, and blue subframe was 5.6 ms, and the data write / erase check time for the liquid crystal panel 21 was 1.4 ms each. At this time, the emission brightness of the backlight 22 alone was 510 cd / m ² , the brightness when white display was performed in combination with the liquid crystal panel 21, was 201 cd / m ² , and the contrast ratio was 83: 1. It goes without saying that the utilization efficiency of the light emission time of the backlight 22 is 100%. The utilization efficiency of the amount of light emitted by the backlight is about 40%, which is a sufficiently high value considering the loss due to the polarizing film. When the power consumption of the backlight 22 was examined, it was 14 / W.

As described above, in the third embodiment, 100% of the light emission time of the backlight 22 can be used, though the driving is slightly complicated as compared with the above-mentioned respective embodiments. In other words, the entire amount of light emitted from the backlight 22 contributes to the light emission display by the liquid crystal panel 21, which is very advantageous when battery driven.

[0080]

As described above in detail, according to the time-division color liquid crystal display device using the ferroelectric liquid crystal of the present invention, the uneven brightness or the display color other than the desired display color is caused in the entire display area. A display device capable of high-quality display such as no color mixing is obtained.

Further, according to the present invention, it is possible to obtain a display which can improve the utilization efficiency of the backlight without lowering the display quality, has low power consumption, is bright, and has excellent display image quality.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of an entire liquid crystal display device of the present invention.

FIG. 2 is a schematic cross-sectional view of a liquid crystal panel and a backlight used in the liquid crystal display device of the present invention.

FIG. 3 is a schematic diagram showing an example of the overall configuration of a liquid crystal display device of the present invention.

FIG. 4 is a schematic diagram showing a configuration example of an LED array.

FIG. 5 is a time chart for explaining the principle of the first embodiment of the display control method for the liquid crystal display device of the present invention.

FIG. 6 is a schematic diagram showing the relationship between the molecular long axis direction (optical axis) of liquid crystal molecules of the liquid crystal display device of the present invention and the directions of the polarization axes of two polarizing films.

FIG. 7 is a time chart for explaining the first embodiment of the display control method for the liquid crystal display device of the present invention.

FIG. 8 is a time chart showing the relationship between the light emission amount of the backlight and the display state of the liquid crystal panel according to the first embodiment of the display control method for the liquid crystal display device of the present invention.

FIG. 9 is a schematic view showing a divided state of a light emitting region of a backlight of the liquid crystal display device of the present invention.

FIG. 10 is a second display control method for a liquid crystal display device according to the present invention.
3 is a time chart for explaining the principle of the embodiment of FIG.

FIG. 11 is a second display control method for a liquid crystal display device according to the present invention.
3 is a time chart for explaining the embodiment of.

FIG. 12 is a third display control method for a liquid crystal display device according to the present invention.
3 is a time chart for explaining the principle of the embodiment of FIG.

FIG. 13 is a third display control method for a liquid crystal display device according to the present invention.
3 is a time chart for explaining the embodiment of.

[Explanation of symbols]

1,5 Polarizing film 6 Light guide plate + light diffusion plate 7 LED array 13 Liquid crystal layer 21 LCD panel 22 Backlight 30 image memory 31 Control signal generation circuit 32 data driver 33 scan driver 35 Backlight control circuit and drive power supply 36 Inverse data generation circuit 37 Selector 40 pixel electrode 41 TFT

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Makino 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited (72) Inventor Yoshinori Kiyota 4-chome, Ueodaanaka, Nakahara-ku, Kawasaki, Kanagawa No. 1 within Fujitsu Limited (56) Reference JP-A-63-85525 (JP, A) Tokuhyo 9-502544 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/133 510 G02F 1/133 535 G09G 3/36

Claims (16)

(57) [Claims] 1. A pair of polarizing plates arranged in directions orthogonal to each other, a liquid crystal panel sandwiched between the polarizing plates, a light source and a rear surface of the liquid crystal panel, and the light source emits light. A switching device corresponding to each pixel of the liquid crystal panel of a liquid crystal display device having a backlight having a light emitting region that guides red, green, and blue light to the liquid crystal panel The backlight is turned on / off during each display cycle corresponding to the data, and the red, green, and blue lights of the backlight are time-divisionally emitted during each display cycle in synchronization with the on / off driving of the switching element. In the display control method for a liquid crystal display device, the first scan for displaying on each pixel of the liquid crystal panel during each period in which the backlight emits red, green, and blue light in a time-division manner. And display The display control method of the liquid crystal display device and performing a second scanning for erasing in this order. 2. The end timing of the first scan and the emission start timing of each color light are aligned, and the start timing of the second scan and the emission end timing of color emission are aligned. 2. A display control method for a liquid crystal display device according to 1. 3. The first scan and the second scan are controlled so that an electric field having the same magnitude but opposite directions is applied to each pixel of the liquid crystal panel. The display control method of the liquid crystal display device according to claim 1. 4. When the electric field is applied to each pixel of the liquid crystal panel in the second scanning, the molecular long axis direction of the liquid crystal molecules is substantially aligned with the polarization axis of either one of the two polarizing plates. The display control method for a liquid crystal display device according to claim 1, wherein the display control method and the display control method according to claim 1. 5. When the electric field is applied to each pixel of the liquid crystal panel in the second scanning, the molecular long axis direction of the liquid crystal molecules is substantially aligned with the polarization axis of one of the two polarizing plates. 2. The display control method for a liquid crystal display device according to claim 1, wherein the polarities of the applied electric fields are controlled so as to coincide with each other. 6. The light emitting area of the backlight is divided into at least two or more, and the light source is divided and driven corresponding to each divided light emitting area of the backlight. A display control method for a liquid crystal display device according to. 7. The backlight is divided so that each divided light emitting area of the backlight is in a light emitting state or a non-light emitting state in synchronization with scanning of each pixel of a corresponding portion of the liquid crystal panel. The display control method of a liquid crystal display device according to claim 6, wherein a light source corresponding to each light emitting region is controlled. 8. The divided light emission of the backlight is such that each divided light emission area of the backlight is in an emission state only while each pixel of a corresponding portion of the liquid crystal panel is in a display state. 7. The display control method for a liquid crystal display device according to claim 6, wherein the light source corresponding to the area is controlled. 9. Two polarizing plates arranged so that their respective polarization axes are orthogonal to each other, and a plurality of liquid crystal pixels sandwiched between the polarizing plates and a plurality of switching elements provided corresponding to each pixel. A liquid crystal panel including an element, a light source, a backlight disposed on the back surface of the liquid crystal panel and configured to emit red, green, and blue light emitted by the light source to the liquid crystal panel, and a backlight, and an image is displayed. Backlight control means for controlling the backlight so that red, green, and blue lights are sequentially output one by one during one frame period, and the backlight emits red, green, and blue lights in a time-division manner. Liquid crystal drive control means for driving and controlling, in this order, a first scan for displaying on each pixel of the liquid crystal panel and a second scan for erasing the display in each period. Specially equipped A liquid crystal display device. 10. The liquid crystal drive control means stores storage means for storing pixel data corresponding to each pixel of the liquid crystal panel of an image to be displayed, and inverse data of each pixel data stored in the storage means. Reverse data generating means for generating, and a first scan and a second scan for each pixel of the liquid crystal panel during each period in which the backlight emits red, green, and blue light in a time division manner. The liquid crystal driving means for performing this sequence and the pixel data stored in the storage means are supplied to the liquid crystal driving means during the first scanning, and the reverse data generated by the reverse data generating means is used for the second data. The liquid crystal display device according to claim 9, further comprising a control unit that supplies the liquid crystal driving unit during scanning. 11. The liquid crystal driving means controls the first scanning and the second scanning so that electric fields having the same magnitude but opposite directions are applied to each pixel of the liquid crystal panel. The liquid crystal display device according to claim 9, wherein the liquid crystal display device is formed. 12. When the electric field is applied to each pixel of the liquid crystal panel in the second scanning, the molecular long axis direction of the liquid crystal molecules is substantially aligned with the polarization axis of one of the two polarizing plates. 10. The liquid crystal display device according to claim 9, wherein the two polarizing plates are arranged so as to substantially coincide with each other. 13. The liquid crystal driving means is arranged such that, when an electric field is applied to each pixel of the liquid crystal panel in the second scanning, the molecular long axis direction of the liquid crystal molecule is one of the two polarizing plates. 10. The liquid crystal display device according to claim 9, wherein the polarity of the applied electric field is controlled so as to substantially coincide with one polarization axis. 14. The light emitting area of the backlight is divided into at least two or more, and the light source is divided corresponding to each of the divided light emitting areas of the backlight. 9. The liquid crystal display device according to item 9. 15. The backlight is divided so that each divided light emitting area of the backlight is in a light emitting state or a non-light emitting state in synchronization with scanning of each pixel in a corresponding portion of the liquid crystal panel. 15. The liquid crystal display device according to claim 14, further comprising backlight emission control means for controlling a light source corresponding to each emission region. 16. The divided light emission of the backlight is such that each divided light emission area of the backlight is in an emission state only while each pixel of a corresponding portion of the liquid crystal panel is in a display state. 15. The liquid crystal display device according to claim 14, further comprising backlight emission control means for controlling a light source corresponding to the area.